Novel Bi2WO6 loaded N-biochar composites with enhanced photocatalytic degradation of rhodamine B and Cr(VI).

In this work we report the production of Bi2WO6 loaded N-biochar composites (BW/N-B) for the removal of rhodamine-B and the reduction of Cr(VI) in water. Biochar was treated with urea to produce a N-modified biochar (N-Biochar), with great conductivity and special 2D sheet platform structure. Materials with different ratios of biochar and urea were produced. These materials were used as platform for supporting Bi2WO6. The characteristics of the as-prepared composites were investigated in detail by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectra (FT-IR), UV-vis diffuse reflectance spectra (UV-DRS), Photoluminescence spectra (PL), Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky curves. After loading N-Biochar, the band gaps of the as-prepared composites were narrower than those of Bi2WO6, which could improve separation and migration of photogenerated electron-hole pairs of BW/B-N under visible-light excitation, enhancing photocatalytic activity. BW/N1-B (ratio of urea to biochar 2:1 and 1 g/L) exhibited excellent photocatalytic activity for the degradation of 10 mg/L Rhodamine B (RhB) (99.1 %, 45 min) and reduction of Cr(VI) (96.7 %, 30 min) under visible-light irradiation. The results will provide a novel theoretical foundation on the application of biochar for photocatalysis and environmental remediation.